I think the zip ties would get tangled in the branches, leaving me with a piece of line that I can’t get up or down anymore.
I have my wife stand at the base of a tree, holding a 10 foot piece of copper or PVC pipe vertically. When I back away far enough, the 10 ft piece of pipe is used to guesstimate how tall the tree is. This works reasonably well and is very quick. For better accuracy I take a picture and then take the ratio of the pipe length to the tree length in the picture to get a more accurate estimate.
For best accuracy, back as far away as you can, while still being able to visually make out the pipe length.